In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there have been, and continue to be, efforts toward scaling down device dimensions (e.g., at submicron levels) on semiconductor wafers. In order to accomplish such high device packing densities, smaller and smaller features sizes are required. To enable such scaling down of device dimensions, sophisticated machines, including spin tracks, are employed in fabricating semiconductors. Such spin tracks can be involved in one or more steps in semiconductor fabrication. Maintaining the spin tracks is important in achieving and maintaining quality in semiconductor manufacturing.
Conventionally, spin tracks may not generate diagnostic information concerning the operation of the machine or, if such diagnostic information is generated, it may be stored locally in the machine, and may require a separate process or machine to analyze the data. Human interactions may be required to determine whether maintenance is required on the spin track. Such interactions may occur locally on each spin track by maintenance personnel of varying skill and experience, resulting in disparate maintenance on spin tracks.
A spin track is a sophisticated machine employed in semiconductor fabrication. A spin track may be employed, for example, for fabrication tasks including, but not limited to, depositing photo resist, depositing oxide, removing edge beads, heating and cooling wafers and cleaning wafers. A spin track may spin a wafer at a high rate of speed to facilitate uniformly coating a wafer with a desired material. A spin track may be damaged by factors including, but not limited to, vibration, contaminated deposition materials, repetitive heating and cooling, electrical surges, build up of deposition and/or cleaning materials, and wear and tear. Such damage can cause the spin track performance to degrade, which impacts the quality of the fabrication step(s) performed by the spin track, with resulting quality degradation in chips fabricated in damaged spin tracks. Since the effects of such damage may be cumulative, rather than acute, regular maintenance can counteract such cumulative effects. In some cases, acute damage to a spin track can cause the machine to cease operation, or to be unable to perform the fabrication step(s) for which it is employed. In such cases immediate maintenance is required to restore the spin track to its operational state.
A spin track may produce diagnostic information concerning its operation including, but not limited to, the number of wafers it has processed, the highest revolutions per minute (rpm) achieved in the spin track, time to achieve a desired rpm (spin up time), time spent at various rpms (spin times), highest temperature achieved in the spin track, time to achieve a desired temperature (heat up time), time spent at various temperatures (heat time), and the number of times automatic cleaning was performed in the spin track.
Conventionally, analyzing diagnostic information if performed at all, required a skilled on site operator to examine the diagnostic information or required the data to be sent (e.g. mailed, faxed) on a periodic basis to a maintenance expert. Rather than scheduling maintenance based on analyses of diagnostic information, maintenance for a sophisticated device like a spin track may have been performed, if at all, on a calendar based system (e.g. machine examined every 12 months) or on an ad hoc basis (e.g. when the machine breaks). As just in time delivery techniques have become more common, such conventional maintenance scheduling has become inadequate. Further, with the increased sophistication and resulting cost of fabrication tools like spin tracks, closer attention to maintenance is required to mitigate performance degradation problems. Thus a system and method is required to facilitate analyzing diagnostic information from spin tracks to enable scheduling routine and special maintenance.
Conventionally, generating feedback and/or feed forward (hereinafter feedback) control information for a sophisticated fabrication device like a spin track, if performed at all, has been performed at the site where the fabrication occurs. But with the increased complexities and costs involved in analyzing the fabrication process data, such feedback control may be foregone, and as a result overall fabrication quality may suffer and thus desired critical dimensions may not be achieved. With the increased requirements for smaller features and higher quality chips, a system and method is required to facilitate generating feedback control information for spin tracks.
The process of manufacturing semiconductors, or integrated circuits (commonly called ICs, or chips), typically consists of more than a hundred steps, during which hundreds of copies of an integrated circuit may be formed on a single wafer. A number of steps performed in a spin track can benefit from a properly maintained spin track. Further, a number of steps can benefit from monitoring and feedback control to ensure quality, including one or more steps performed in or by a spin track.
The requirement of small features with close spacing between adjacent features requires sophisticated manufacturing techniques, including high-resolution photolithographic processes. Fabricating a semiconductor using such sophisticated techniques may involve a series of steps including cleaning, thermal oxidation or deposition, masking, developing, etching, baking and doping. Each such step may require active monitoring and feedback. One or more such steps may be performed in or by a spin track, and thus a system and method for monitoring the maintenance status of such spin tracks is required to facilitate fabricating chips that meet desired critical dimensions.
Wafers may be pre-cleaned using, for example, high-purity, low-particle chemicals. One or more cleaning steps may be performed in a spin track. The silicon wafers may be heated and exposed to ultra-pure oxygen in diffusion furnaces under carefully controlled conditions to form a silicon dioxide film of uniform thickness on the surface of the wafer. Once clean, layers of oxide and photo resist are deposited on the wafer. The layers may be deposited in or by a spin track. To facilitate achieving desired critical dimensions, the oxide should be applied in a uniform manner resulting in a layer with a substantially planar surface. The oxide may be applied in a spin track. To facilitate desired oxide application, a properly function, well-maintained spin track is important. Thus, a system and method for monitoring diagnostic data, for feeding back control information and for scheduling routine and special maintenance is required.
The masking step is used to protect one area of the wafer while working on another area. This process is referred to as photolithography or photo-masking. A photo resist, or light-sensitive film, is applied to the wafer, giving it characteristics similar to a piece of photographic paper. To facilitate achieving desired critical dimensions, the photo resist should be applied in a uniform manner resulting in a layer with a substantially planar surface. The photo resist is typically applied in a spin track. To facilitate desired photo resist application, a properly functioning, well-maintained spin track is important. Thus, a system for monitoring diagnostic data, for feeding back control information, and for scheduling routine and special maintenance on a spin track is required.